The inorganic perhydrate bleach most widely used in laundry detergent compositions is sodium perborate in the form of either the monohydrate or tetrahydrate. However, concerns about the impact of boron salts on the environment have led to an increasing interest in other perhydrate salts, of which sodium percarbonate is the most readily available.
Detergent compositions containing sodium percarbonate are known in the art. Sodium percarbonate is an attractive perhydrate for use in detergent compositions because it dissolves readily in water, is weight efficient and, after giving up its available oxygen, provides a useful source of carbonate ions for detergency purposes.
On the other hand, the use of amylase enzymes in detergent compositions is known, although such use has been mainly described in perborate-based formulations.
The use of enzymes, including amylase in percarbonate-based compositions is known from e.g. JP 57028197; PCT/US93/06302 and PCT/US93/06877.
Although the action of amylase on starch-based stains in particular, is known, and the action of percarbonate on bleacheable stains is also known, it has now been surprisingly discovered that the combined use of percarbonate and amylase at specific ratios provides a synergetic effect on the removal of difficult stains such as starch-based stains and blood stains, in particular at low temperatures.
In addition such a synergetic removal effect is also seen on particulate stains such as peat clay, mud, fertilizing soil, high organic content clay.
It has further been found that the ternary system consisting of percarbonate/amylase/protease at specific ratios provides an even better result on the above stains, in particular on starch-based and blood stains.